I have two Activity with button, that switch between it
Intent intent1=new Intent(Act1.this,Act2.class);
startActivity(intent1);
and
Intent intent1=new Intent(Act2.this,Act1.class);
startActivity(intent1);
If I switch ten times by button, how much Activites will I have?
If I push back on device button, I can see ten different state Act1 or Act2.
This depends on the launch mode of your activities. Look at this page.
But by default you will have the initial activity and 10 new instances -> 11 activities.